At some point, common sense comes into this discussion.

We have evidence that life on Earth thrives in almost every conceivable environment.

We have evidence that life develops from simple forms to complex ones, and that adaptation to changes in the environment occur at every level (but especially the simple forms).

We have evidence that complex molecules form under many conditions, including deep space.

We have evidence now that planets aren't a weird exception in solar systems, but a rule.

Earth is the only place proven to have life on it so far, but to me it seems obvious that given the number of potential life locations out there, it's silly to assume we are the only place it ever happened. It's like someone discovering the ocean for the first time, then seeing a fish jump nearby. What are the odds in all that ocean that no other fish exist?

Now, if you want to go into life being rare or common, that's another discussion.